A brush seal arrangement of the above mentioned general type is known in the art, for example from German Patent Laying Open Document 3,907,614, in which a brush seal is fixedly, i.e. non-rotationally, secured to the stator, while the bristles extend toward and into the circumferential gap between the rotor and the stator so as to concentrically surround the rotor axis.
Brush seals are predominantly used in turbine machines, and especially gas turbine engines, to provide a seal with the minimum possible leakage at circumferential gaps, for example between a machine housing and rotor or around a rotary shaft of the turbine machine, between two spaces having different prevailing fluid pressures within the turbine machine. Generally, the bristles of the brush seal are held and guided so as to be elastically yieldable or movable in order to compensate for any eccentric or oscillation motions of the rotor or shaft relative to the housing, which may result, for example, from rotor imbalances or the like. To achieve this, the brush seal bristles are generally oriented in a substantially radial direction so that the bristles can deflect or bend laterally to achieve the above mentioned compensating effect.
In this context, brush seals have been recognized as advantageous over the previously long utilized labyrinth seals, because such labyrinth seals can only adapt themselves to eccentric shaft movements to a very limited degree. Furthermore, brush seals advantageously distinguish themselves over prior labyrinth seals by their insensitivity to various contaminants that might be present in the fluid medium that is to be sealed, by their lower production costs, and by their lower total weight.
In rotor-stator arrangements having only a very small radial space available in which a brush seal is to be installed, it has been problematic or even impossible to use the previously known brush seals having radially directed seal bristles, due to their relatively great radial structural height and corresponding radial installation space requirements. In this context, if it is simply attempted to shorten the length of the bristles in order to reduce the radial space requirement, difficulties arise because the flexibility of the bristles and thus the compensating yieldability of the brush seal is lost. In order to avoid this problem, yet still reduce the radial dimension of a seal, German Patent Laying-Open Document 3,828,833 discloses an arrangement using a seal ring that is supported or mounted on elastically flexible rods or spring elements arranged coaxially around the rotor. A fixed end of the respective rods is secured to the stator, while a free end of the respective rods carries the seal ring that is arranged coaxially about the rotor. This seal ring, together with the circumferential surface of the rotor, forms a seal gap as a primary seal. It is disadvantageous in this known arrangement, that a seal ring is still needed to achieve the seal, and that a relatively great effort is required for securing the fixed ends of the flexible rods in the stator and the other ends in the seal ring.